package lanQiaoBei.基础算法.sort;
import java.util.*;
/*
* “求一个数的发三次方根”——浮点二分
* */
public class P7 {
    public static void main(String[] args)throws Exception {
          Scanner scanner= new Scanner(System.in);
          double x=scanner.nextDouble();
          double l=0,r=x;
          while(r-l>1e-8){
              double mid=(l+r)/2;
              if(mid*mid*mid<=x)l=mid;
              else r=mid;
          }
         System.out.println(l);
    }
}
